1. Field of the Invention
The present invention relates to a hardener for an alkali metal silicate, and to its use in the foundry industry.
2. Description of the Prior Art
U.S. Pat. No. 3,137,046 discloses the preparation of foundry cores and foundry molds using a ternary mixture comprising 93 to 98 parts by weight of a sand suitable for the foundry industry, 2 to 7 parts by weight of an aqueous solution of an alkali metal silicate and a stoichiometric amount, relative to the silicate, of an alkylene carbonate having from 2 to 7 carbon atoms in the alkylene radical. Molds having satisfactory mechanical properties are obtained by this method. It is also known, from French Published Application No. 2,264,608, to use dialkyl esters of diacids (formulae 1 of Tables I and II). Unfortunately, the use of these hardeners suffers from the disadvantage of giving excessively high setting times.
Thus, there exists a need in the art for hardeners for use in the foundry industry which avoid the aforementioned disadvantage while, at the same time, insuring the production of foundry molds and cores exhibiting good mechanical properties.